In the related art, a post-processing apparatus performs various types of post-processing for one or more sheets on which an image is formed by an image forming apparatus. One type of the post-processing apparatus has a function to staple a bundle of sheets. However, the bundle of stapled sheets may cause a trouble when the sheets are put into a shredder without the staples being removed. Further, when the stapled sheets are used in an image forming apparatus after staples are removed, holes made by the staples may cause jamming of sheets.